'She'll never walk the streets again'

The sister of Christchurch man Philip Nisbet, who was fatally poisoned by his wife, has vowed that his killer will never walk the streets of New Zealand again.

Lee-Anne Cartier, who was instrumental in focusing suspicion on Helen Milner, after police had initially concluded the death was a suicide, held her brother's ashes during the sentencing and said afterwards that he can now rest in peace.

"He's got closure, we've got closure, she's got a life sentence, I will attend every Parole Board hearing, and she will never walk the streets of New Zealand again."

In the High Court at Christchurch on Thursday, Milner was sentenced to life imprisonment with a minimum non-parole period of 17 years for murdering her husband. The 50-year-old kept her head bowed and didn't react when the sentence was announced.

In his sentencing, Justice Gendall said it was a carefully planned murder out of which Milner stood to gain financially. He said she poisoned Mr Nisbet with an overdose of an antihistamine to which he was allergic in order to get his $250,000 life insurance payout.

The judge said she initially covered up the crime by making it look like a suicide. He said he had to send her to prison for at least 17 years because of the premeditated nature of the killing.

"There could hardly be a clearer case of calculated pre-planning and premeditation," Justice Gendall said.

Milner also received six years' imprisonment for attempted murder and will serve that sentence concurrently.

Earlier, Mr Nisbet's family read emotional victim impact statements to the court. His younger brother, Andrew Nisbet, broke into tears as he told the court that he was very close to his brother and Milner had robbed them of a future together.

His 81-year-old mother, Yvonne Nisbet, said the pain of losing her son has broken her heart and some days she cannot get out of bed because she has lost the will to live.

Authenticity of suicide note questioned

At Milner's trial in December last year, Crown prosecutor Kathy Basire told the court that after Mr Nisbet's death Milner had shown several people a suicide note supposedly written and signed by him.

After some of those people questioned the authenticity of the signature, she gave police another suicide note without the handwritten signature and with different content. She was also alleged to have sent herself a suicide text from her husband's phone.

The court also heard that Milner had earlier tried to recruit her sons to help kill her husband. Ms Basire told the jury Milner had spoken to her son Greg Kearns in 2009 and offered him $20,000 of the insurance money to get rid of her husband, but he declined.

Ms Basire also said Milner spoke to her other son, Adam Kearns, about hiring a hitman.

Sister-in-law had her suspicions

Ms Cartier told the court she had begun to suspect Milner in June 2009. She said she started contacting friends and associates of Milner and Mr Nisbet to share her theories and began to forward all correspondence to police.

Police had initially concluded that the case was one of suicide, but after a coroner found in 2011 that Mr Nisbet's death was unlikely to have been self-inflicted, they began a second investigation.

Once the jury found Milner guilty, it was revealed that she was already in prison for perverting the course of justice, serving a sentence of two years and eight months for sending text messages to herself, pretending they were from her son Adam.

The texts were sent in an effort to make it look like her son was breaching a restraining order. The Parole Board said it was a calculated effort to have her son imprisoned.

Previously suppressed papers also showed that Milner had convictions for theft from an employer.

Reimbursement offer rejected

Ms Cartier has rejected a police offer to reimburse her for costs incurred while investigating her brother's death.

Detective Inspector Tom Fitzgerald says she has indicated she's not happy with the offer and wants to pursue wider compensation.